The present invention relates to improvements to digital, electric, length or angle-measuring instruments of the type which include means for generating analog periodic primary measurement signals, and means for accommodating errors in phase, amplitude, and the like in these primary signals.
The resolution limit of such a measuring instrument is determined in part by the grid constant of the incremental division used. In the past, a number of attempts have been made to increase the resolution of measuring instruments to a value greater than that of the grid constant of the division. In particular, electronic means have been used for this purpose. When such interpolation is performed, it is important that the analog primary signals be as free of error as possible in order to allow accurate interpolation.
German DE-OS 27 29 697 discloses the use of a micro-computer to correct previously digitized analog signals and then to calculate interpolation values from the corrected analog signals. The calculating time of the micro-computer determines the maximum speed of movement in the measuring process when this approach is used.